Anaxagoras was the first known atheist. He also introduced the concept of νούσ (nous, or mind), the ordering force behind the Universe. But he did not take this idea any further.[2]

He held that the Sun was not a god, but just material. It was a "red-hot mass many times larger than the Peloponnese". The Moon was a solid body with geographical features, and made of the same substance as the Earth.[3]

Anaxagoras was eventually arrested and prosecuted for freethought. He was banished from Athens for impiety in 450 BC. However, his works were available in Socrates' day for a drachma.[4]